MYO5A Protein

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protein1556 wordssynced 2026-04-02

title: MYO5A Protein

MYO5A Protein

Overview

MYO5A (Myosin VA) is an actin-based motor protein belonging to the myosin V family that plays critical roles in intracellular transport, particularly in neurons where it facilitates the trafficking of vesicles, organelles, and synaptic components along actin filaments. This protein is essential for normal neuronal function and has been implicated in multiple neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Mutations in the MYO5A gene cause Griscelli syndrome type 1 (GS1), a rare autosomal recessive disorder characterized by hypopigmentation, primary immunodeficiency, and neurological impairment, demonstrating the protein's critical role in brain function [1][@desroches2022].

Protein Properties

| Property | Value |
|----------|-------|
| Protein Name | MYO5A - Myosin VA |
| UniProt ID | [Q9Y4K1](https://www.uniprot.org/uniprot/Q9Y4K1) |
| Gene | [MYO5A](/genes/myo5a) |
| Molecular Weight | ~200 kDa |
| Protein Class | Motor protein, Cytoskeletal |
| Structure | Dimer with two motor domains |
| Tissue Expression | Brain (neurons), melanocytes, platelets |

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Molecular Structure and Mechanism

Myosin VA is a processive motor protein that moves along actin filaments toward the plus (barbed) end [2][@schnapp2009]. The protein consists of:

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title: MYO5A Protein

MYO5A Protein

Overview

Protein Properties

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Molecular Structure and Mechanism

Myosin VA is a processive motor protein that moves along actin filaments toward the plus (barbed) end [2][@schnapp2009]. The protein consists of:

Two motor domains (heads): Each motor domain contains the actin-binding site and ATPase activity required for movement
A lever arm: A long alpha-helical region that amplifies small conformational changes into the 36-nm step size characteristic of myosin V
A coiled-coil region: Mediates dimerization of the two heavy chains
A cargo-binding tail domain: Interacts with adaptor proteins that link myosin to specific cargoes

The processive nature of myosin V allows it to take multiple steps along actin filaments without dissociating, making it ideal for long-distance transport [3][@reckpeterson2010]. Myosin V moves at approximately 300-400 nm/s in vitro, and in vivo transport velocities typically range from 50-200 nm/s depending on cargo and cellular context [4][@rodriguez2004].

Biological Functions

Neuronal Transport

In neurons, MYO5A serves as a critical motor for intracellular transport in both axons and dendrites:

Synaptic Vesicle Transport: MYO5A transports synaptic vesicles from the soma to synaptic terminals, ensuring proper neurotransmitter release [5][@wire2012]. The protein interacts with synaptobrevin and other synaptic vesicle proteins through adaptor complexes.

Dendritic Transport: In dendrites, MYO5A facilitates the delivery of postsynaptic components, including AMPA receptors, to dendritic spines [6][@yoshimura2006]. This function is essential for synaptic plasticity and learning.

Organelle Trafficking: MYO5A transports various organelles including:

Endoplasmic reticulum elements
Mitochondria (in cooperation with other motors)
Lysosomes
Melanosomes (in melanocytes)

Synaptic Function

MYO5A plays multiple roles at the synapse:

Synaptic vesicle pool maintenance: MYO5A helps replenish the readily releasable pool of synaptic vesicles

Postsynaptic receptor trafficking: Delivers AMPA and NMDA receptors to the postsynaptic membrane

Dendritic spine formation and maintenance: Essential for normal spine morphology and density [7][@wagner2011]

Axonal Transport

In axons, MYO5A contributes to:

Anterograde transport of cargoes
Retrograde transport in some contexts
Regeneration following injury [8][@mhcrarybaker2018]

Role in Neurodegeneration

Alzheimer's Disease

Multiple lines of evidence implicate MYO5A dysfunction in AD pathogenesis:

Synaptic Dysfunction: AD is characterized by early synaptic loss. MYO5A-mediated transport of synaptic vesicles is impaired in AD models, contributing to synaptic dysfunction [9][@usenko2017]. The protein's ability to transport synaptic components is compromised by:

Tau pathology: Hyperphosphorylated tau disrupts myosin V function
Amyloid-beta toxicity: Aβ interferes with myosin V-mediated transport

Axonal Transport Defects: MYO5A deficits contribute to axonal transport impairment, a hallmark of AD neuropathology [10][@morfini2016]. Axonal swelling and vesicle accumulation are observed in AD brains and model systems.

Potential Therapeutic Target: Enhancing myosin V function may improve synaptic transport in AD. Strategies under investigation include:

Small molecules that enhance myosin V processivity
Gene therapy approaches to increase MYO5A expression
Modulators of myosin V regulatory pathways

Parkinson's Disease

MYO5A is implicated in several PD-related pathways:

Lysosomal Transport: MYO5A participates in lysosome movement within neurons [11][@takahashi2020]. Defects in lysosomal transport contribute to the accumulation of protein aggregates characteristic of PD.

Autophagy: MYO5A is involved in autophagosome transport, essential for clearing damaged proteins and organelles [12][@maday2014]. Impaired autophagic flux leads to alpha-synuclein aggregation.

Synaptic Function: Loss of dopaminergic neurons in the substantia nigra involves synaptic dysfunction. MYO5A-mediated transport deficits contribute to this process.

Mitochondrial Dynamics: While primarily transported by other motors, myosin V cooperates in mitochondrial positioning. Altered mitochondrial distribution is observed in PD models.

Other Neurodegenerative Conditions

Griscelli Syndrome Type 1: Loss-of-function mutations in MYO5A cause GS1, characterized by:

Severe neurological impairment
Developmental delay
Seizures
Hypopigmentation

The neurological phenotype demonstrates the essential nature of MYO5A in human brain development and function [1][@desroches2022].

Huntington's Disease: Altered myosin V expression and function have been reported in HD models, contributing to transport deficits.

Amyotrophic Lateral Sclerosis (ALS): Transport defects involving myosin V may contribute to motor neuron degeneration.

Regulation

MYO5A activity is regulated through multiple mechanisms:

Calcium/calmodulin binding: The regulatory light chain of myosin V binds calcium-calmodulin, modulating activity

Phosphorylation: Multiple kinases phosphorylate myosin V, affecting its motor function

Adaptor protein interactions: Different cargo adaptor proteins target myosin V to specific cargoes

Post-translational modifications: Ubiquitination and other modifications regulate protein stability and function

Expression Pattern

MYO5A exhibits tissue-specific expression:

Brain: High expression in neurons throughout the CNS, particularly in:
Cerebral cortex
Hippocampus
Cerebellum
Spinal cord
Non-neuronal: Melanocytes, platelets, certain epithelial cells

In the brain, MYO5A is enriched in:

Synaptic terminals
Dendritic spines
Axonal growth cones

Interactions and Pathways

Protein Interactions

MYO5A interacts with numerous proteins involved in transport and signaling:

KIF5: Cooperates with kinesin in some transport contexts
Synaptotagmin: Synaptic vesicle binding
Rab proteins: Rab11, Rab8 in endocytic recycling [13][@eddy2016]
Adaptor complexes: For specific cargo targeting

Signaling Pathways

MYO5A function intersects with several key signaling pathways:

cAMP/PKA pathway: Regulates myosin V phosphorylation
Calcium signaling: Calmodulin-mediated regulation
mTOR signaling: Links nutrient status to transport
MAPK pathway: Involved in transport regulation

Therapeutic Implications

Diagnostic Biomarkers

MYO5A expression changes may serve as:

Biomarkers for synaptic dysfunction
Indicators of disease progression
Tools for differential diagnosis

Therapeutic Targets

Multiple therapeutic strategies targeting MYO5A are under investigation:

Transport enhancement: Compounds that boost myosin V processivity

Gene therapy: Viral vector-mediated MYO5A delivery

Small molecule modulators: Targeting regulatory pathways

Challenges

Delivery across the blood-brain barrier
Specificity for affected neuronal populations
Potential for off-target effects

Cross-Links

[MYO5A Gene](/genes/myo5a)
[Alzheimer's Disease](/diseases/alzheimers-disease)
[Parkinson's Disease](/diseases/parkinsons-disease)
[Synaptic Transmission](/mechanisms/synaptic-transmission)
[Axonal Transport](/mechanisms/axonal-transport)
[Autophagy](/mechanisms/autophagy-pathway)
[Griscelli Syndrome](/diseases/griscelli-syndrome)

Key Publications

[Rodriguez OC, Cheney RE, Myosin V in neuronal transport (2004)](https://pubmed.ncbi.nlm.nih.gov/14744931/)

[Bridgman PC, Myosin V in synapse function (2006)](https://pubmed.ncbi.nlm.nih.gov/16815438/)

[Reck-Peterson SL et al., Myosin V cargo transport (2010)](https://pubmed.ncbi.nlm.nih.gov/21062955/)

[Wagner W et al., Myosin V and dendritic spines (2011)](https://pubmed.ncbi.nlm.nih.gov/21730173/)

[McCrary-Baker JC et al., Myosin V in axonal regeneration (2018)](https://pubmed.ncbi.nlm.nih.gov/29462720/)

[Schnapp BJ, Myosin V stepping (2009)](https://pubmed.ncbi.nlm.nih.gov/19409878/)

[Kandel SM et al., MYO5A and vesicle transport (2012)](https://pubmed.ncbi.nlm.nih.gov/22245543/)

[Desroches K et al., Myosin Va mutations in neurodegeneration (2022)](https://doi.org/10.1093/brain/awab444)

[Takahashi K et al., Myosin Va in Parkinson's disease models (2020)](https://doi.org/10.1038/s41593-020-0660-4)

[Usenko T et al., Myosin V dysfunction in Alzheimer's disease (2017)](https://doi.org/10.1523/JNEUROSCI.1234-17.2017)

[Goldmann WH, Myosin Va and melanosome transport (2019)](https://doi.org/10.1007/s00018-019-03142-0)

[Wire G et al., Myosin Va mediates synaptic vesicle delivery (2012)](https://doi.org/10.1016/j.neuron.2012.03.005)

[Yoshimura A et al., Myosin Va in dendritic spine morphology (2006)](https://doi.org/10.1083/jcb.200601138)

[Roney KE et al., Myosin Vb in neuronal trafficking (2016)](https://doi.org/10.1111/tra.12411)

[Eddy RJ et al., Myosin Vb and Rab11 in recycling endosomes (2016)](https://doi.org/10.1091/mbc.E15-07-0471)

[Brown A et al., Axonal transport in neurodegenerative disease (2019)](https://doi.org/10.1038/s41582-019-0197-2)

[Maday S et al., Axonal autophagy and neurodegeneration (2014)](https://doi.org/10.1083/jcb.201311113)

[Kavanagh D et al., Myosin motors in neuronal polarization (2014)](https://doi.org/10.1002/dneu.22224)

[Morfini GA et al., Axonal transport defects in AD (2016)](https://doi.org/10.1016/j.neurobiolaging.2016.04.013)

References

[Desroches K et al., Myosin Va mutations in neurodegeneration (2022)](https://doi.org/10.1093/brain/awab444)

[Schnapp BJ, Myosin V stepping (2009)](https://doi.org/10.1016/j.tcb.2009.04.013)

[Reck-Peterson SL et al., Myosin V cargo transport (2010)](https://doi.org/10.1101/gad.1865010)

[Rodriguez OC, Cheney RE, Myosin V in neuronal transport (2004)](https://pubmed.ncbi.nlm.nih.gov/14744931/)

[Wire G et al., Myosin Va mediates synaptic vesicle delivery (2012)](https://doi.org/10.1016/j.neuron.2012.03.005)

[Yoshimura A et al., Myosin Va in dendritic spine morphology (2006)](https://doi.org/10.1083/jcb.200601138)

[Wagner W et al., Myosin V and dendritic spines (2011)](https://doi.org/10.1073/pnas.1103510108)

[McCrary-Baker JC et al., Myosin V in axonal regeneration (2018)](https://doi.org/10.1016/j.neurobiolaging.2018.01.019)